This application requests a continuation of funding for an ongoing clinical trial (1R01 DE12204-05). The project is funded for a five-year period, ending 03/31/03. A five-year maximum limitation to funding was available at the time of application. The Special Emphasis Panel providing the scientific review for the original protocol recommended expansion of the investigation to incorporate a forth treatment period. This recommendation extended the original timeline to six years. For this reason the project was planned to extend beyond the five-year period and a competitive renewal was anticipated. Secondarily, the project has encountered additional delays. A nearly one year interruption resulted from Virginia Commonwealth University IRB compliance problems that stopped grant activities during this time. Finally due to a combination of an already tight timeline and the reality of the actual time necessary to schedule and provide prerequisite surgical and prosthodontic treatment relative to that allocated in the original proposal, the project has encountered an additional delay of nearly one year. The projected completion date is now 03/31/06. This project utilizes 30 subjects in a prospective, randomly assigned clinical study that uses a four-period, six sequences, three treatments crossover design to test the hypothesis that defined outcomes of variable implant overdenture treatments are equivalent. The project tests three overdenture treatment modalities, (1) four-implant, bar/clip-attached treatment, (2) two-implant, bar/clip-attached treatment, and (3) two-implant independently attached (O-ring) treatment. Each subject has four dental implants placed into the anterior mandible and new dentures are fabricated. After successful implant integration, subjects are randomly assigned to one of six sequences of treatment. Each treatment is followed for data collection for at least twelve months before the mandibular denture is modified to incorporate the next treatment in the sequence. Equivalence is measured in terms of prosthesis retention, stability, supporting and peri-implant tissue response, patient satisfaction/preference and treatment complications/failures. Presently the study is well underway and successfully proceeding. There are no dropouts, all subjects have been recruited, consented, completed dental implant surgical procedures. All but one subject have completed prosthodontic complete denture and implant bar fabrication and have received at least their first randomly assigned treatment. A number of subjects have moved from the first to their second treatment. The project's external Data and Safety Monitoring Board has routinely met to review project status and their reports have encouraged project completion and have promoted this application process for continuation of funding. [unreadable] [unreadable] [unreadable]